Electric circuit breaker



June 23, 1942. c. THUMIM ET AL 2,287,578

ELECTRIC CIRCUIT BREAKER Filed Aug. 28, 1940 Inventor-'5: Car-l Thumim,John D. Sager;

6W) b W 5 Their Attor'ne5.

Patented June 23, 1942 UNITED STATES, PATENT OFFICE ELECTRIC CIRCUITBREAKER Carl Thumim, mm, and John D. Gayer, Lansdowne, Pa., assignors toGeneral Electric Company, a corporation of New York Application August28, 1940, Serial No. 354,698

Claims.

Our invention relates to electric circuit breakers and more particularlyto improvements in electric circuit breakers of the gas-blast type.

In order to eliminate the the hazard, circuit breakers have beendesigned which do not utilize oil or other inflammable liquid forarc-extinguishing purposes but instead employ ablast of fluid, such asair or other gas, to extinguish the -arc formed both when the circuit isbroken between the relatively movable contacts of the circuit breakerand also during the closing operation 01' the circuit breaker to preventthe formation of any are at'this time. Circuit breakers havingindependent opening and closing fluid blasts are disclosed and claimedin United States Letters Patent 2,218,797, granted October 22, 1940, onthe joint application of Leonard J. Linde and Torild Andersen and inapplication Serial No. 317,564, filed Jointly on behalf of Carl ThumimEdward J. Frank and Alexander 0. Boisseau on February 6, 1940.

It will be understood by those skilled in the art that gas-blast circuitbreakers require gasstorage facilities, the size of which is mainlydependent upon the gas used for the gas blast for arc-extinguishingpurposes. From a cost standpoint, it would be desirable to limit thesefacilities to a minimum and this can be accomplished by conserving thegas required for the fluid blast. We have discovered that, during thecircuit-opening operation of a gas-blast circuit breaker, the gas blastshould exist at the instant the contacts separate and continue for alonger period of time than would be required during the circuit-closingoperation where it is merely necessary to prevent the arc from strikingand not necessary to extinguish an arc. Due to these desireddiilferences, both in the time of initiation and the duration of thegasblast, a. considerable saving of gas under pressure and, consequently,storage facilities and the like results if independently adjustablemeans are provided for controlling the opening and closing gas blasts ofelectric circuit breakers of the gas-blast type.

Accordingly, it is an object of our invention to provide an improvedcircuit breaker of the gas-blast type with independently adjustablemeans for controlling the gas blast during both the opening and theclosing movements of the circuit breaker.

It is a further object of our invention to provide a new and improvedcircuit breaker of the fluid-blast type in which the initiation and theduration of both the opening and closing fluid able, whereby aneconomical consumption of fluid results and the fluid-storage facilitiesmay be maintained within reasonable limits.

Further objects and advantages of our invention will become apparent asthe following description proceeds and the features of novelty whichcharacterize our invention will be pointed out with particularity in theclaims annexed to and forming a part of this specification.

For a better understanding of my invention, reference may be had to theaccompanying drawing in which Fig. 1 is a schematic diagram partly insection illustrating my invention, and Fig. 2 is an enlarged perspectiveview of a portion of the apparatus shown in Fig. 1.

Referring now to the drawing, we have illustrated a gas-blast circuitbreaker I0 connected to a source of fluid under pressure H through ablast valve generally indicated at l2. A fluid motor l3 associated witha trip-free mechanism generally indicated at H is provided for producingrelative movement between the contacts of circuit breaker Ill and alsoto charge an energystorage means for causing high-speed opening of thecircuit breaker. A suitable pivoted assembly and associated mechanismgenerally indicated at l5 and embodying our invention is provided forcontrolling the operation of blast valve l2 and, consequently, the fluidblast during both the opening and closing movements of the circuitbreaker it).

Although our invention is applicable to polyphase or single-phasecircuit breakers, We have illustrated our invention schematically inFig. 1 as applied to a polyphase circuit breaker l0, only the structureassociated with one set of contacts for one pole Illa of the circuitbreaker being shown since the other poles of the circuit breaker areidentical. Where We have illustrated any operating mechanism for thevarious phases or poles which are identical for each phase or pole, suchparts are hereinafter characterized by the same reference numerals withthe subscript a, b, or 0, depending upon the par blasts areindependently and accurately adjustnecting the arc-confining chamber,associated which is shown is described and broadly claimed in the jointapplication of David C. Prince, William K. Rankin, and Wilfred F.Skeats, Serial No. 303,126, filed November 6, 1939, and assigned to thesame assignee as the present application, and is illustrated by way ofexample only.

The mechanism for interconnecting the movable contacts Ila, etc.,hereinafter referred to as contacts I1 of the circuit breaker I0, onlyone pole of which has been shown, with the trip-free mechanism generallyindicated at I4 and the fluid motor I3 comprises separate operating rods2I a, 2Ib, etc., one for each pole of the breaker, and each having oneend thereof respectively connected to the corresponding movable contactsI1. These individual operating rods 2Ia, 2Ib. etc., are each connectedto one end of suitable levers 22a, 2217, etc., each having-the otherends 4 thereof provided respectively with crossheads 23a, 22b, etc.,arranged to slide in crosshead guides 24a, 241), etc. Suitable buffers25a, 2522, etc., respectively are provided for each of the links 22a,22b, etc., to cushionthe closing movement of the operating mechanism andassociated circuit breaker III. Each of the links, such as 22aand 22b,has an intermediate point thereon pivotally connected to one end of bellcranks 26 and 21, respectively, which, in turn, are pivotallymounted onfixed supports 26' and 21'. In order that themovable contacts I1associated used only to close circuit breaker III and charge springs 29and 30, it is desirable to provide suitable means for returning piston34 to its initial position at the right-hand end of cylinder 33 afterthe closing operation is completed. Accordingly, I have shown a suitablereturn spring 31 mounted in a housing 38 supported by cylinder 33.Suitable ports 39 in housing 38 allow air in cylinder 33 to the left ofpiston 34 to escape when circuit breaker I0 is being closed.

The trip-free thrust-transmitting structure generally indicated at I4can be of any suitable design, the one shown by way of examplecomprising a main toggle 4Il-4I including the roller 36 which coactswith the torque-transmitting rod associated with piston 34. The togglelink'49 is pivotally connected at one end to a lever 42 supported on afixed pivot 43. The toggle link M, on the other hand, isconnected at 44to one end of a lever 45 supported on a fixed pivot 46.

The other end of lever 45 is connected through a link 41 to bell crank26. The pivot 48 of toggle,link is normally held fixed by a suitabletripping means including an extension 42 on lever 42 supporting a roller49 which coacts with the tripping latch 50 pivotally mounted at 5|. Whenthe toggle 404I is straightened at its knee joint 52 byforce-transmitting rod 35, the lever is rotated about its fixed pivot 46in a counterclockwise direction to cause the rod'28 to move toward theright to the position shown in with all the poles of circuit breaker IDare si- 'multaneou sly actuated, all the bell cranks such as 26 and 21are interconnected by a horizontally reciprocating operating rod 28.

As mentioned above, fluid motor I3 is provided for closing circuitbreaker I0 and charging the energy-storage means which cause highspeed"opening of the circuit breaker;

These energy-storage means are illustrated" in Fig. 1 as comprising anopening spring 29 and a balancing'spring 30. Opening spring 29 isarranged to operate rod 3|, which engagesv with a roller 32 attached toan extension 21" of bell crank 21.

When these springs are charged, as shown in Fig.

1, they tend to cause counterclockwise rotation of bell crank 21 and,consequently, also of bell crank 26- and any other bell cranks which areconnected together through horizontally reciprocating operating rod28-which moves toward the to cause movement of rod 28 and bell crank 21and any other bell cranks connected theretoto Fig. 1 when the circuitbreaker is closed. When the latch is moved out of restraining engagementwith respect to roller 49, the lever 42 is free to pivot in a clockwisedirection. The toggle 40-4I is then no longer in thrust-transmittingposition and is free to collapse, permitting movement toward the left ofrod 28 under the bias of the energy-storage means comprising openingspring29 and balancing spring 30.

In Fig. 1, the trip-free thrusttransmitting linkage I4 is illustrated inthe restraining or closed position with respect to rod 28. In thisposition, the knee joint 52 of toggle 404I is overset and engages a stopmember 53. The linkv age is therebyeffectively locked inthis positionwith respect to any opening thrust tending to move rod 28 toward theleft as long as the pivot 48 and toggle link 40 are held fixed by theabovedescribed tripping means. When latch 50 of the tripping means nolonger restrains link 42 and. hence, also pivot 48, the former rotatesin a clockwise direction under the influence of the react-. ingforcestending to cause opening movement of horizontally reciprocating rod 28.,When the toggle 4II--4I has collapsed and the lever, 45

is rotated in a clockwise direction, opening of circuit breaker II)results through the upward movement of operating rods 2Ia, 2"), etc.

Because of the high opening speed of circuit breaker Ill, it isdesirable to provide cushioning means. for retarding the openingmovement so as to prevent any damage to the moving parts thereof.Accordingly, we have shown a suitable dashpot 54 connected to apivotally mounted link 55 having a roller 56 at one end thereof which isarranged to engage with a suitable cam surclose the respective contactsI6 and I1 of circuit breaker I 9.

The fluid motor I3 is shown in Fig. 1 at the instant whencircuit-breaker III has just been completely closed. Since this fluidmotor I3 is face 51 provided on bell crank 26. The dashpot 54 and camsurface 51 may be so designed that any desired opening characteristic isobtained. For example, it may be desirable to design cam surface 51 soas to provide an arrangement similar to that disclosed and claimed inUnited States Letters Patent 1,904,539, granted April 18, 1933, upon anapplication of Sigwart Ruppel.

In order to operate fluid motor l3, cylinder 99 thereof is connected tosource II through a solenoid-operated valve 59 which may be of anysuitable type and is schematically illustrated as of thebalanced-pressure pilot-valve type such as is disclosed in the copendingapplication of Carl Thumim, Serial No. 343,002, filed June 28, 1940.

Blast valve I2 is alsoschematicallydllustrated as of thebalanced-pressure pilot-valve type comprising pilot valve 59 and, asdescribed and broadlyclaimed in the above-mentioned copendingapplication, Serial No. 343,002, is so arranged as to be opened toinsure a blast of fluid adjacent the contacts of circuit breaker Illprior to any opening movement thereof. Accordingly, we

slots 88 and 69 for adjustably supporting closing gas-blast cam I andopening gas-blast cam II,

respectively. A suitable guide cam I2 is rigidly v inafter, is suitablysupported by a lever I4 which have illustrated blast valve I2 ascontrolling a V valve 69 for interconnecting the source of fluid underpressure with a pneumatic tripping means generally indicated at 6|. Itwill be observed from Fig. 1 that circuit breaker III cannot be openedunless latch 50 is rotated so as to release lever 42. Thepneumatic'tripping means Si is provided, as is obvious from the drawing,to cause clockwise rotation of latch 50 at the desired time so thatcircuit breaker III may open after a blast of fluid is assured adjacentthe separating contacts thereof. This tripping means comprises apiston-operated plunger 62 arranged toengage an extension on latch 50whenever fluid under pressure moves plunger 62 toward the right, asshown in Fig. 1. By thisarrangement, tripping of circuit breaker I0cannot occur until blast valve I2 is at least partially open so thatvalve 60 is open and the condition of the fluid pressure is such as toallow satisfactory interruption of the circuit. a

Blast valve l2, as will be understood by those skilled in the art, iscaused to open upon opening of pilot valve 58 which may be operated whenan abnormal current condition occurs in the electrical circuitassociated with circuit breaker I0 requiring the circuit to beinterrupted. Accordingly, opening of circuit breaker I9 is initiated bymeans of a solenoid 63 operatively connected to pilot valve 59, whichsolenoid is energized for operation in response to abnormal currentconditions from source 64 which may, for example, be connected to acurrent transformer, not shown,

connected in the associated power circuit, also not shown. Thearrangement described heretofore is not our invention but is describedand broadly claimed in copending applicationSerial No. 343,002 referredto above. Our invention is specifically concerned with the mechanicalmeans, used in conjunction with a gas-blast circuit breaker, operable inresponse to the position of the contacts of circuit breaker III fortiming the opening gas blast and initiating and timing the closing gasblast as will be described hereinafter, and is an improvement on thearrangement disclosed in copending application Serial No. 343,002.

In order mechanically to operate pilot valve 59 to time the opening airblast for circuit breaker I0 and to initiate and time the closing airblast, we have provided a pivoted assembly and asso-' ciated mechanismgenerally indicated at I5, which is shown in detail in Fig. 2. Asuitable pivotally mounted cam supporting plate 85 is provided, whichmay be rigidly bolted to one of the bell cranks such as 26 or 21 ifdesired, or, as illustrated in the drawing, may be mounted on shaft 66which is operatively connected to horizontally reciprocating operatingrod 29 through link 91. Cam-supporting plate 65 is provided with arcuateis pivotally supported at I5 by U-shaped crank member I6. A pair ofmutually opposing springs 11 are provided to hold lever "in a neutralcentral ,position between the laterally extending portions of U-shapedcrank member I6 which is pivotally mounted at I8 to a supporting memberI9. A suitable biasing spring 89 coacting with supporting member I9 and-U-shaped crank I6 tends to cause cam follower roller 13 to engage withcam-supporting plate 65.

Cam follower roller I8 coacts with either closing gas-blast cam III oropening gas-blast cam II depending upon whether roller guide pin 8|attached to lever 14 coacts with the upper cam surface 'I2a or lower camsurface 12b respectively, of guide cam I2. Pivotal movement ofcamsupporting plate 65 in response to the relative movement'between thecontacts I6 and I! of circuit breaker II) will, thereby cause camfollower roller I3 to engage with either closing gas-blast, cam 10 oropening gas-blast cam II, whereupon U-shapedv crank I6 is caused torotate about its supporting pivot I8 in a counterclockwise directionwith reference to Fig. 2. By means of a suitable linkage comprisinguniversal joint 82, link 93, bell crank 84 pivotally supported at 85,and tension rod 86 operatively connected at 81 to pilot valve 59, thecounterclockwise rotation of U-shaped crank 16 about its supportingpivot I8 causes opening of pilot valve 59 and, consequently, opening ofblast valve I2.

The point during the opening and closing strokes of circuit breaker IIIat which closing and opening gas-blast cams l0 and II become effectivemay be suitably adjusted by the position of these cams on cam-supportingplate 65. For

- this purpose, we have provided bolts 88 and 89.

The length of the opening and closing air blasts may also be adjusted byusing interchangeable cams of various lengths for cams I0 and H.

As was mentioned above, the opening air blast is initiated by means ofsolenoid 63, after which the timing thereof is controlled by the pivotedassembly generally indicated at I5 and more specincally by openinggas-blast cam II. In order to render solenoid 63 ineifective to controlpilot valve 59 after mechanical control of pilot valve 59 is obtained byvirtue of opening gas-blast cam 'I.I,'we have provided a suitable switch90 connected in series with the energizing circuit of solenoid 63 whichis closed wh circuit breaker III is closed by-means of a cam, member 9|suitably supported on shaft 66 which is arranged to engage one of themembers of switch 90 in this position. After a predetermined openingmovement of circuit breaker I0 when mechanical control of pilot valve 59has been obtained, cam 9| has rotated sufliciently so that spring 92 maycause opening of switch 90 and, consequently, deenergization of solenoid63'.

In view of valve 60, which is openedafter blast valve I2 has been openeda predetermined amount, it will be observed that circuit breaker I0could never be closed without additional means since, as soon as the airblast during the closing stroke thereof was initiated, fluid underpressure would be admitted to pneumatic-tripping means 6| by virtue ofthe opening of valve direction.

4 68 and, consequently, tripping latch 88 would release the trip-freemechanism; generally indicated at IL In order to prevent this, we havevprovided a suitable vaive 88 operable by means of a solenoid 88 theenergizing winding of which is connected in parallel with the energizingwindthe solenoid-operated valve flhwhereupon fluid motor 18 throughtrip-free thrust-transmitting linkage ll moves horizontallyreciprocating opering of solenoid 68. Valve 88 is arranged to be cuitbreaker l8, and for a short period during the opening-stroke thereofuntil switch 88 has been opened; During the closing stroke of circuitbreaker 18, therefore, when blast valve l2 and, consequently, valve 68are open ,valve 88 remains closed and, hence, pneumatic-tripping means6| is not effective.

The operation of the circuit breaker described above will be obvious tothose skilledin the art in view of the detailed description set forthabove as well as the description set forth in copending applicationSerial No. 343,002 referred to above. With the circuit breaker in theclosed position shown in Fig. 1, opening thereof is initiated byenergization of solenoid 68 and solenoid 84 through switch 88 which isin the closed position. This energization might occur by virtue of anabnormal current condition on the associated power circuit or bysuitable manual means, not shown. Energiza tion of solenoid 68 willcause opening of pilot valve 58 and, consequently, open-' ing of blastvalve 12 to insure a blast of fluid from source adjacent the contacts l6and ll of cir- As soon as blast valve l2 opened a predetermined amount,valve 68 opens,

cuit breaker l8.

and, since solenoid 84 has opened valve 83, the

. piston-operated plunger 62 of tripping means 6| is actuated'togeleasethe trip-free thrust-transmitting mechanism H, thereby allowing openingof circuit breaker l8 under the influence of opening spring 28. It willbe understood that a blast of fluid under pressure adjacent the contactsmust occur prior to opening of circuit breaker N by pneumatic-trippingmeans 6|. As the circuit breaker l8 begins to open, horizontallyreciprocating rod 28 moves toward the left in Fig. '1 causing rotationof shaft 66 and, consequently, of cam-supporting plate 65 in acounterclockwise counterclockwise rotation of cam-supporting plate 86,the beveled right end 12b of cam guide 12 engages guide pin 8| and pullslever ll down- Shortly after the. beginning of the wardly so that camfollowerroller 13 engages opening gas-blast cam ll, causing a clockwiserotation of U-shaped crank "about pivot 18 so that pilot valve 85 isheld open mechanically by virtue of the linkage comprising members 88 to86. Cam 8|, which is also rotatable 'with shaft 66, allows switch 88 tobreak the circuit for'energizing solenoids 63 and 84 as soon asmechanical control of pilot valve 68 is obtained. As the opening motionof circuit breaker l8 continues, cam follower roller 13 rolls down theleft incline of opening gas-blast cam ll whereupon spring ating rod 28toward the right which, consequently, also causes movement ofcam-supportin Plate 65. During this closing operation. guide pin 8|rides up cam surface 12a, of guide cam I2 so that cam follower roller 13engages with closing gasblast cam I8 at a predetermined point during theclosing stroke of circuit breaker N to cause opening of pilot valve 88and, consequently, of

gas-blast valve I! in .-the same manner as described in connection with.opening gas-blast valve H. The duration of this gas blast is, of course,dependent upon the length of cam 18 and, when the contacts l6 and I! ofcircuit breaker l8 engage, pilot valve 58 and, consequently, air-blastvalve II are closed and lever 14 is restored to its neutral position bymeans blast valve |2 will be operated by virtue of opening gas-blast cam1| in time to extinguish the are drawn so that even though a greaterdeterioration-of the.contact parts might take place under suchconditions, the circidt will be interrupted and, hence, an additional!factor of safety is provided.

It will be understood that a considerable saving in fluid and,consequently, in fluid-storage facilities may be obtained by theindependent adjustment of .the'opening and closing gas-blast cams sothat not only may the point at which the air blast is initiated becontrolled but also the duration of the respective air blasts.

It will be apparent to those skilled in the art that our invention isnot limited to the particular construction shown but that changes andmodifications may be made without departing from the spirit and scope ofour invention and we aim in the appended claims to cover all suchchanges and modifications.

What we claim asnew and desire to secure by Letters Patent of the UnitedStates, is:

1. man electric circuit breaker of the fluidblast type comprising aplurality of relatively movable contacts, means for producing relativemovement between said contacts, a source of opening fluid blast,meansfor causing opening.

' of said valve for a period of time during said means 88 forcesU-shaped crank 16 to closepilot valve 58 and, consequently, gas-blastvalve I2 is closed. Guide pin 8| is thereafter released by guide cam 12so that lever 14 is restored to its neutral position by mutuallyopposing-springs 11.

If circuit breaker I8 is in the open position, closing thereof may beinitiated by energizing circuit-closing[operation to produce a closingfluid blast and means including a pivoted assembly having mountedthereon two independently adjustable means for adjusting the durationand time of initiation of said opening and closing fluid blasts.

2. In an electric circuit breaker of the gasblast type comprising meansdefining an arc chamber, relatively movable contacts separable to drawan arc in said chamber, a source of gas under pressure for supplying agas blast to said arc chamber, valve means for controlling the flow ofgas from said source to said are chamber, means for operating saidcontacts to open and closed circuit positions, and means including apivoted assembly having mounted thereon two independently adjustablecams for operating said valve means in accordance with the position ofsaid relatively movable contacts so that said valve means is opened fora period of time during the opening movement of said contacts which isindependent of the period of time that said valve means is opened duringthe closing movement of said contacts.

3. In an electric circuit breaker of the fluidblast t pe comprisin aplurality of relatively movable contacts, means for producing relativemovement between said contacts, a source of fluid under pressure, valvemeans associated with said source for producing a blast of fluid ad-Jacent said contacts during both the circuit-interrupting andcircuit-closing operations of said circuit breaker, a plurality of cammeans for controlling said valve means so that the fluid blast duringthe circuit-interrupting operation is independent of the fluid blastduring the circult-closing operation, and means for determining which ofsaid cam means is eifective to control said valve means.

4. In an electric circuit breaker of the gasblast type comprising meansdefining an arc chamber, relatively movable contacts separable to drawan arc in said chamber, a source of gas under pressure for supplying agas blast to said are chamber, valve means for controlling the flow ofgas from said source to said arc chamber,

means for operating said contacts to open and closed circuit positions,a plurality of cam means for controlling said valve means in accordancewith the position of said relatively movable contacts so that said valvemeans is operated for a period of time during the opening movement ofsaid contacts which is independent of the period of time that said valvemeans is operated during the closin movement of said contacts, and meansincluding a guide cam for rendering one of said cam means effective tocontrol said valve means.

5. In an electric circuit breaker of the fluidblast type comprisingmeans defining an arc chamber, relatively movable contacts separable todraw an arc in said chamber, a source of fluid under pressure forsupplying a fluid blast to said are chamber, valve means for controllingthe flow of fluid from said source to said are chamber, means foroperating said contacts to open and closed circuit positions, meansincluding a pivoted assembly operable in response to the relativemovement of said contacts, said pivoted assembly including an openingfluid-blast cam and a closing fluid-blast cam, means arranged to engageeither said opening or said closing fluid-blast cam to operate saidvalve means to produce a blast of fluid in said chamher, and meansincluding a guide cam for determining which of said cams is effective tocontrol said valve means.

6. In an electric circuit breaker of the fluidblast type comprising aplurality of relatively movable contacts, means for producing relativemovement between said contacts, a source of fluid under pressure, valvemeans associated with said source for producing a blast of fluidadjacent tion of said valve means, fault responsive means for initiatingthe operation of said valve means, means including a pivoted assemblyinterposed between said valve means and said means for producingrelative movement between said contacts for timing the opening of saidvalve means during the circuit-interrupting operation and independentmeans associated with said pivoted assembly for controlling said valvemeans during the circuit-closing operation.

7. In an electric circuit breaker of the fluidblast type comprising a,plurality of relatively movable contacts, means for producing relativemovement between said contacts, a source of fluid under'pressure, valvmeans associated with said source for controlling the flow of a blast offluid adjacent said contacts, fault-responsive means for initiating theoperation of said valve means to permit a blast of fluid to flowadjacent said contacts during the circuit-interrupting operation, meansfor controlling the duration of said fluid blast, and means forrendering said fault-responsive means ineffective after saidlastmentioned means has taken over control of the duration of said'fluidblast.

8. In an electric circuit breaker of the fluidblast type comprising aplurality of relatively movable contacts, means for producing relativemovement between said contacts, a sourceof fluid under pressure, valvemeans associated with said source for controlling the flow of a blast offluid adjacent said contacts during both the circuit-interrupting andthe circuit-closing operations of said circuit breaker, fault-responsivemeans for initiating the operation of said valve means to permit a blastof fluid to flow adjacent said contacts during the circuit-interruptingoperation, means including a pair of cams, one for controlling theduration of the fluid blast during the circuit-interrupting operationand the other for controlling said valve means during thecircuit-closing operation, and means for rendering said fault-responsivemeans ineffective after said last-mentioned means has taken over controlof the duration of said fluid blast during the circuit-interruptingoperation.

9. In an electric circuit breaker of the fluidblast type comprising aplurality of relatively ,movable contacts, means for producing relativemovement between said contacts, a source of fluid under pressure, valvemeans associated with said source for producing a blast of fluidadjacent said contacts during both the circuit-interrupting andcircuit-closing operations of said circuit said contacts during both thecircuit-interruptbreaker, a pair of cam means for controlling said valvemeans so that the fluid blast during the circuit-interrupting operationis independent of the fluid blast during the circuit-closing operation,means for normally rendering said pair of cam means ineffective, andmeans responsive to the relative movement between said contacts fordetermining which of said cam means is effective to control said valvemeans.

10. In an electric circuit breaker of the fluid- 1 blast type comprisingmeans defining an arc chamber, relatively movable contacts separable todraw an arc in said chamber, a source of fluid under pressure forsupplying a fluid blast to said are chamber, valve means for controllingthe flow of fluid from said source to said are chamber, means forproducing relative movementbetween said contacts, means including apivoted assembly rotatable in response to the relative movement betweensaid contacts, said pivoted assembly including an opening fluid-blastcam and a said cams, and means including a guide cam for rendering oneor the other of said cams eflective to control said valve meansdepending upon the direction of rotation of said pivoted assembly.

ARL 'IHUMIM. JOHN D. GAYER.

